I want to pull results from a database into a select dropdownbox. What I want to do is have a select dropdown box that shows the selected value that is in the database along with the other values in the list. The field CommDeptID and DeptText in the CommDept Table has values in it like 1 HR, 2 Administration, 3 IT etc. LocationID equals CommDeptID.
I am getting this error:
Cannot implicitly convert type 'System.Linq.IQueryable<>' to 'IntranetSite.Models.Communications'. An explicit conversion exists (are you missing a cast?)
Communications is my Model That looks like this:
[Key]
public int CommunicationsID { get; set; }
[Required(ErrorMessage = "Enter Title")]
public string Title { get; set; }
[Required(ErrorMessage = "Select Location")]
public int LocationID { get; set; }
[Required(ErrorMessage = "Select Message Type")]
public int MessageTypeID { get; set; }
[Required(ErrorMessage = "Enter Message")]
public string Message { get; set; }
public DateTime EnteredDateTime { get; set; }
LocationID is a field in my Communications table and a field in my CommDept Table.
[Key]
public int CommDeptID { get; set; }
public string DeptText { get; set; }
My code:
var data = from c in _Context.Communications
join d in _Context.CommDept on c.LocationID equals d.CommDeptID
where c.CommunicationsID == id
select new
{
c.CommunicationsID,
c.Title,
c.MessageTypeID,
c.Message,
c.LocationID,
d.DeptText
};
Communications = data;
LocationID = _Context.CommDept
.Select(a => new SelectListItem
{
Value = a.CommDeptID.ToString(),
Text = a.DeptText,
Selected = a.CommDeptID == c.LocationID
})
.ToList();
Your select new statement is creating a new anonymous type. Then you are trying to implicitly cast that into the Communications model. Instead of just saying select new, try to select a new instance of the specific type instead of an anonymous type.
Another issue is that you are not using the data returned from the Linq statement. And then you are trying to use the alias c from the top linq query in a new statement. I would combine them into one statement.
Assuming LocationID is a SelectList, try the following:
var myList = new SelectList(new List<SelectListItem>{
from c in _Context.Communications
join d in _Context.CommDept
on c.LocationID equals d.CommDeptID
where c.CommunicationsID == id
select new SelectListItem
{
Value = d.CommDeptID.ToString(),
Text = d.DeptText,
Selected = d.CommDeptID == c.LocationID
}
}.ToList());
I didn't run this myself, so double-check the code. You can see more information here too: How to generate dropdownlist in asp.net MVC razor
Related
I have a product sales data and want to show the summary of sale grouped by product id.
Summary result should show product name and total sales. How can I select a field along with groupby result and that field is not the key field.
public partial class SaleOrderDetail
{
public int Id { get; set; }
public int ProductId { get; set; }
public string ProductName { get; set; }
public int Quantity { get; set; }
public decimal Price { get; set; }
public decimal LineTotal { get; set; }
}
var query = from saleorder in _dbContext.SaleOrderDetail
group saleorder by saleorder.ProductId into salesummary
select new
{
productid = salesummary.Key,
prdouctname = salesummary.First().ProductName,
totalqty = salesummary.Sum(s => s.Quantity)
};
I got the error invalidoperationException because of First() for product name.
You have to include ProductName in grouping Key.
var query =
from saleorder in _dbContext.SaleOrderDetail
group saleorder by new {saleorder.ProductId, saleorder.ProductName} into salesummary
select new
{
productid = salesummary.Key.ProductId,
prdouctname = salesummary.Key.ProductName,
totalqty = salesummary.Sum(s => s.Quantity)
};
Making SaleOrderDetail as AsEnumerable() did the trick. For SQL Expression it will work if make it as AsEnumerable() or .ToList<> etc.
var query = from saleorder in _dbContext.SaleOrderDetail.AsEnumerable()
group saleorder by saleorder.ProductId into salesummary
select new
{
productid = salesummary.Key,
prdouctname = salesummary.First().ProductName,
totalqty = salesummary.Sum(s => s.Quantity)
};
Using EF Core 2.2.2, I have a table in my database which is used to store notes for many other tables. In other words, it's sortof like a detail table in a master-detail relationship, but with multiple master tables. Consider this simplified EF Model:
public class Person
{
public Guid PersonID { get; set; }
public string Name { set; set; }
}
public class InvoiceItem
{
public Guid InvoiceItemID { get; set; }
public Guid InvoiceID { get; set; }
public string Description { get; set; }
}
public class Invoice
{
public Guid InvoiceID { get; set; }
public int InvoiceNumber { get; set; }
public List<Item> Items { get; set; }
}
public class Notes
{
public Guid NoteID { get; set; }
public Guid NoteParentID { get; set; }
public DateTime NoteDate { get; set; }
public string Note { get; set; }
}
In this case, Notes can store Person notes or Invoice notes (or InvoiceItem notes, though let's just say that the UI doesn't support that).
I have query methods set up like this:
public IQueryable<PersonDTO> GetPersonQuery()
{
return from p in Context.People
select new PersonDTO
{
PersonID = p.PersonID,
Name = p.Name
};
}
public List<PersonDTO> GetPeople()
{
return (from p in GetPersonQuery()
return p).ToList();
}
public IQueryable<InvoiceDTO> GetInvoiceQuery()
{
return from p in Context.Invoices
select new InvoiceDTO
{
InvoiceID = p.InvoiceID,
InvoiceNumber = p.InvoiceNumber
};
}
public List<InvoiceDTO> GetInvoices()
{
return (from i in GetInvoiceQuery()
return i).ToList();
}
These all work as expected. Now, let's say I add InvoiceItems to the Invoice query, like this:
public IQueryable<InvoiceDTO> GetInvoiceQuery()
{
return from p in Context.Invoices
select new InvoiceDTO
{
InvoiceID = p.InvoiceID,
InvoiceNumber = p.InvoiceNumber,
Items = (from ii in p.Items
select new ItemDTO
{
ItemID = ii.ItemID,
Description = ii.Description
}).ToList()
};
}
That also works great, and issues just a couple queries. However, the following:
public IQueryable<InvoiceDTO> GetInvoiceQuery()
{
return from p in Context.Invoices
select new InvoiceDTO
{
InvoiceID = p.InvoiceID,
InvoiceNumber = p.InvoiceNumber,
Items = (from ii in p.Items
select new ItemDTO
{
ItemID = ii.ItemID,
Description = ii.Description
}).ToList(),
Notes = (from n in Context.Notes
where i.InvoiceID = n.NoteParentID
select new NoteDTO
{
NoteID = n.NoteID,
Note = n.Note
}).ToList(),
};
}
sends a separate query to the Note table for each Invoice row in the Invoice table. So, if there are 1,000 invoices in the Invoice table, this is sending something like 1,001 queries to the database.
It appears that the Items subquery does not have the same issue because there is an explicit relationship between Invoices and Items, whereas there isn't a specific relationship between Invoices and Notes (because not all notes are related to invoices).
Is there a way to rewrite that final query, such that it will not send a separate note query for every invoice in the table?
The problem is indeed the correlated subquery versus collection navigation property. EF Core query translator still has issues processing such subqueries, which are in fact logical collection navigation properties and should have been processed in a similar fashion.
Interestingly, simulating collection navigation property with intermediate projection (let operator in LINQ query syntax) seems to fix the issue:
var query =
from i in Context.Invoices
let i_Notes = Context.Notes.Where(n => i.InvoiceID == n.NoteParentID) // <--
select new InvoiceDTO
{
InvoiceID = i.InvoiceID,
InvoiceNumber = i.InvoiceNumber,
Items = (from ii in i.Items
select new ItemDTO
{
ItemID = ii.ItemID,
Description = ii.Description
}).ToList(),
Notes = (from n in i_Notes // <--
select new NoteDTO
{
NoteID = n.NoteID,
Note = n.Note
}).ToList(),
};
LINQ Query not populating
Model extract is as follows
public class ServiceBulletin
{
[Key]
public int Id { get; set; }
public virtual ICollection<ServiceBulletinProducts> ApplicableProducts { get; set; }
}
public class ServiceBulletinProducts
{
[Key]
public int Id { get; set; }
public int ServiceBulletinId { get; set; }
public virtual Product Product{ get; set; }
}
I'm using the following code at the moment to populate a collection
var x = from m in _dc.ServiceBulletins.Include(p => p.ApplicableProducts)
.Include(m => m.Manufacturer)
where m.DeleteStatus == DeleteStatus.Active
select m;
var x1 = new List<ServiceBulletin>();
foreach (var item in x)
{
var p = from m1 in _dc.ServiceBulletinsProducts.Include(p2=>p2.Product)
where m1.Product.DeleteStatus == DeleteStatus.Active &&
m1.ServiceBulletinId == item.Id
select m1;
var p99 = p.ToList();
item.ApplicableProducts = p99;
x1.Add(item);
};
So this is intended to have a Parent Child relationship and I’m trying to do a query which populates a collection of ServiceBulletins with a ApplicableProducts item with a fully populated collection of ServiceBulletinProducts for the ServiceBulletin with the values of the Product populated
The collection is populated but the ServiceBulletinProducts are always set to null and I can’t seem to add an Include such as .Include(p => p.ApplicableProducts.Products) to try and populate the product details – which is resulting in me iterating around the collection to populate the items.
Am I missing something to enable the population on the 1st query for the Include statement or do I need to do the query in a different way ?
Figured out the following should do the trick.
var x = from m in _dc.ServiceBulletins.Include(p => p.ApplicableProducts.Select(p2=>p2.Product))
.Include(m => m.Manufacturer)
where m.DeleteStatus == DeleteStatus.Active
select m;
I have two table in the same DataContext as follows.
Table PersonnelInfo
{
personnelId,
personnelName ,
description,
deathMonthYear,
updatedBy,
updatedAt
}
Table PersonnelInfoOther
{
personnelId,
personnelName ,
updatedBy,
updatedAt
}
I define a class as follows:
public class PersonnelInfoAll
{
public short personnelId{get;set;}
public string personnelName { get; set; }
public string personnelNameOtherLan { get; set; }
public string description { get; set; }
public string deathMonthYear { get; set; }
public int updatedBy { get; set; }
public DateTime updatedAt { get; set; }
}
I need to left join first table with the second one and retrieve all the data as PersonnelInfoAll format:
public List<PersonnelInfoAllLan> GetPersonnelInfosAll()
{
var context = new BookDataClassesDataContext { ObjectTrackingEnabled = false };
var personnelInfo = from u in context.PersonnelInfos
join b in context.PersonnelInfoOtherLans
on u.personnelId equals b.personnelId
select new PersonnelInfoAllLan
{
personnelId = u.personnelId,
personnelName = u.personnelName,
personnelNameOtherLan = b.personnelName,
description = u.description,
deathMonthYear = u.deathMonthYear,
updatedBy = u.updatedBy,
updatedAt = u.updatedAt
};
return personnelInfo.ToList();
}
This gives me only one row which matches with both. But I need all the records from the first table. Is there any one to help.
Use group join:
var personnelInfo = from p in context.PersonnelInfos
join l in context.PersonnelInfoOtherLans
on p.personnelId equals l.personnelId into g
from l in g.DefaultIfEmpty()
select new PersonnelInfoAllLan
{
personnelId = p.personnelId,
personnelName = p.personnelName,
personnelNameOtherLan = (l == null ? null : l.personnelName),
description = p.description,
deathMonthYear = p.deathMonthYear,
updatedBy = p.updatedBy,
updatedAt = p.updatedAt
};
If there no match in lans for some person, then DefaultIfEmpty() will return null from joined group. That's why you need to check l for null.
I've written a LINQ query shown below :
List<Actions> actions = resourceActions.Actions.Select(s => s.ActionName).ToList();
How do I give for selecting multiple columns here ? ie I want to add columns s.ActionId and s.IsActive. I'm unable to apply it.
Make a class to represent the data you want:
public class ResourceAction
{
public int Id {get;set;}
public string Name {get; set; }
}
Select a list of those instead:
List<ResourceAction> actions = resourceActions.Actions
.Select(s => new ResourceAction() { Id = s.Id, Name = s.ActionName}).ToList();
I believe this is what your looking for. However you need to change the output to an anonymous type.
var actions = resourceActions.Actions.Select(s => new { s.ActionName, s.ActionId, s.IsActive } ).ToList();
You can use a anonymous type for this, for example
var actions = resourceActions.Actions.Select(s =>
new { Id = s.Id, Name = s.ActionName, Active = s.IsActive).ToList();
but a better way would be to create a class like
public class ActionWithId
{
public int Id { get; set; }
public string Name { get; set; }
public bool Active { get; set; }
}
List<ActionWithId> actions = resourceActions.Actions.Select(s =>
new ActionWithId() { Id = s.Id, Name = s.ActionName, Active = s.IsActive }).ToList();